The development of the Internet has significantly changed the way people live and interact with each other. Interaction is the basis for building trust and may therefore also be influenced by the Internet. This study investigated whether Internet use influences people’s social trust, accounting for the perception of fairness and social support, using the latest data from the CGSS from China. The results showed that Internet use has a significant negative predictive effect on the level of social trust, and the perception of social fairness plays a fully mediating role in this relationship. That is, Internet use can indirectly reduce people's level of social trust by reducing their perception of social fairness. Furthermore, the results indicated that social support can moderate people's perceptions of social fairness and thus mitigate the negative effects of Internet use on social trust. These results suggested that we should raise the profile of the impact of internet use, actively improve people's perceptions of social fairness to increase their level of social trust, and finally, focus on the positive role of social support, which can reduce the negative impact of internet use.